It is generally believed that the decrease in granulocytes usually begins one week after the cessation of chemotherapy, reaching its lowest point 10-14 days after cessation, maintaining at a low level for 2-3 days before slowly rising, and returning to normal by the 21st-28th day, forming a U-shape. The decrease in platelets appears slightly later than the decrease in granulocytes, also reaching its lowest value around two weeks, with a rapid decline, a short stay at the bottom, and then a rapid rise, forming a V-shape. The decrease in red blood cells appears even later.

The pattern of bone marrow suppression after chemotherapy has the following significance:

(1) It limits the interval time of chemotherapy courses. Theoretically, chemotherapy should be administered at the strongest dose in the shortest time to quickly inhibit or kill tumor cells. However, the recovery of bone marrow suppression after chemotherapy takes time, so many chemotherapy sessions are conducted every 3-4 weeks;

(2) It involves the handling of grade 2 bone marrow suppression. It is a consensus that intervention must be given for grade 3 and 4 bone marrow suppression, but it is confusing when to intervene and when to observe briefly for grade 2 bone marrow suppression. Utilizing the above pattern helps in decision-making (described later);

(3) It helps in early detection of bone marrow suppression. Based on the pattern of bone marrow suppression after chemotherapy, this problem can be detected early and handled accordingly. Checking the blood routine every two days after chemotherapy can achieve this purpose.

Currently, the grading of bone marrow suppression after chemotherapy adopts the World Health Organization's grading standards for acute and subacute toxic reactions to anticancer drugs. For granulocyte suppression, the absolute value of neutrophils is more important than the total number of white blood cells.

Note two key points: one is when the absolute value of neutrophils is less than 1×10^9/L, and the other is when the platelet count is less than 50×10⁹/L.

These are the critical points for grade 3 granulocytopenia and grade 3 thrombocytopenia, signals of potential complications, and indications for intervention.